My First Tube Amp

presbystrat · 02-23-2010, 05:14 PM

Hi Guys, it's been a while since I've posted around here. I got my first real amp today; a Fender Blues Jr. I got a barely used one for $340 with the shipping. Having a great time with it. Very versatile. I'm not sure why people mod the hell out of these things because it sounds great stock. Those power tubes do seem to run hot though; I don't know if the biasing mod would be worthwhile or if it would change the sound any. I might consider building an attenuator for it but I don't think I need any pedals with this thing.

ibanez_dude · 02-23-2010, 05:42 PM

I personally haven't done it, but I've been thinking about doing it for a while.

**thesteve** · 02-23-2010, 06:01 PM

One thing to consider is that tube amps are hot to begin with. Since this is your first, what might seem hot to you may be normal operation.

I've always thought to compare tubes to lightbulbs in terms of heat intensity.

relient nelson · 02-23-2010, 06:06 PM

Steve, Blues Jrs do get super hot.

presbystrat · 02-23-2010, 07:02 PM

Quote:

Originally Posted by thesteve

I've always thought to compare tubes to lightbulbs in terms of heat intensity.

Probably a good comparison since they both are glass enclosed vacuum with tungsten elements. I would say the preamp tubes are hot like light bulbs bulbs but the power tubes are hot as a soldering iron. When I touched them briefly, they left grill marks on my finger.

relient nelson · 02-23-2010, 11:45 PM

Okay well, mine don't get that hot... well, actually, maybe they do. I've never touched my power tubes right after playing. All I know is that the combo gets really hot overall after a good half hour of playing.

Major Tom · 02-24-2010, 04:29 AM

Congrats

Yeah, power tubes do get hotter than preamp tubes. I don't remember getting any grill marks, but I don't think I've ever grabbed one at full temperature. Even after cooling down for a few minutes they can be too hot to pull them out.

One of the Lpad attenuators, like in the home made attenuators sticky thread IMO would be very useful for that amp, and I think you would find it more significant and useful than most mods. Those also get pretty hot, so you need to mount it on a bracket to keep it away from tolex, cords, and fingers; a good place to put them is in the back of the cab with the knob accessible. I made mine with an input jack and an output cord with plug, so that the plug from the speakers plugs in to the attenuator, and then the attenuator plugs into the speaker out jack on the amp. That way you can easily disconnect it if neccessary, although they way they are made, when you turn it full up CW, it is out of the circuit and passing the full speaker signal with no attenuation.

What is the biasing mod you are referring to - changing to cathode bias, or lowering / raising the bias?

Ax · 02-24-2010, 10:18 AM

That's fairly normal. You could always check the biasing. A lot of times they come a bit hot out of the box, at least both of mine did for my taste, but a quick bias fixes all.

My adjustments however, were minute, leaving a bit of a difference, but not much. Mostly in the sound. I can't tell the difference in temperature.

relient nelson · 02-24-2010, 01:45 PM

Quote:

Originally Posted by Major Tom

What is the biasing mod you are referring to - changing to cathode bias, or lowering / raising the bias?

I know that BillM always lowers the bias because it's cooking the tubes quite a bit more than necessary.

presbystrat · 02-27-2010, 07:08 AM

This thing is still amazing me. I've always thought that the answer to good tone at low volume was using a digital modeler. Not So! I think my RP250 may be going up on the auction block soon. It just sounds harsh and digital now. I have tried the BJ many times in the past in music stores but it never quite had this impression on me. I guess I really had to be able to have the time to get comfortable with it at home to find the sound I have been looking for. I've been keeping the fat switch engaged because it does sound a little bright and thin without it. I've been playing through my repertoire of praise songs and it's like experiencing them all in a new way. I'm living in an apartment temporarily so I haven't really been able to crank this thing, but I will be able to do that at the end of the month when we move into our new house.